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==Actions==
==Actions==
===Chemotaxis===
When injury occurs, macrophages are needed at the site itself to perform the functions that the body needs it to do.
===Phagocytosis===
===Phagocytosis===
<p>Macrophages are [[Phagocytosis|phagocytic]] and take up particles and cell debris by endocytosis, as well as engulfing pathogens like bacteria through the specialist function of [[Phagocytosis|phagocytosis]]. These are then present in the macrophage inside phagosomes. Lysosomes present in the cytoplasm then bind with the phagosome and release their contents which degrade/digest its contents. The degradation of the lysosomal contents occurs in much the same way as [[Neutrophils|neutrophils]] with both oxygen-dependent and oxygen-independent mechanisms.</p>
<p>Macrophages are [[Phagocytosis|phagocytic]] and take up particles and cell debris by endocytosis, as well as engulfing pathogens like bacteria through the specialist function of [[Phagocytosis|phagocytosis]]. These are then present in the macrophage inside phagosomes. Lysosomes present in the cytoplasm then bind with the phagosome and release their contents which degrade/digest its contents. The degradation of the lysosomal contents occurs in much the same way as [[Neutrophils|neutrophils]] with both oxygen-dependent and oxygen-independent mechanisms.</p>
====Recognition====
<p>To function correctly neutrophils need to correctly identify material that is either foreign (non-self) or which requires removal, such as damaged cells. They are able to recognise some foreign material directly but in other circumstances proteins (opsonins) that bind to bacteria are required to increase the chances of successfully binding the foreign material to the neutrophil. Some examples of opsonins include [[Complement|complement]] component C3bi and bound [[Immunoglobulins|antibody]]. </p>
====Killing====
<p>This occurs using either oxygen dependant pathways or oxygen independent pathways.</p>
<p>Oxygen dependant killing requires the production of reactive oxygen species (ROS)(O<sub>2</sub><sup>-</sup>), hydrogen peroxide (OH), reactive nitrogen species (RNS) (nitric oxide (NO)) and chlorine (Cl*) free-radicals that damage bacterial membranes (OH + Cl* = HOCl (otherwise known as bleach!)) . These reactive species are generated during a burst of respiration following [[Phagocytosis|phagocytosis]] where increased amounts of oxygen are produced. Hydrochloric acid (HCl) is also produced during this process.</p>
<p>Oxygen independent killing uses lysosomes, cathepsin (a protease) and other mechanisms. Lysozymes are particularly effective against gram positive bacteria as they hydrolyse the glycopeptide coating of the bacterial organisms. </p>
===Antigen Presentation===
===Antigen Presentation===